14 THE MAKQUETTE TRON-BEAKINC} UlSTEICT. 



Rogers, H. J). Verbal coinmuuicatiou to tlie Boston Society of ^Natural 

 History, April 1, 1S40. Proc. Boston Soe. Nat. Hist., Vol. II, pages 12.4-125. 



Ill tlu' same year in which Grray wrote, Professor Rogers, in a verbal 

 communication to the Boston Society of Natural History, gave an account 

 of the mode of occm-rence of copper at Keweenaw Point, and discussed the 

 age of the sandstones and conglomerates of the Lake Superior region. In 

 the course of his remarks he announced the discovery of a contact between 

 a red sandstone and an underlying series of sandstones which he thought 

 to be the equivalent of the Primal sandstone and slate of the Appalachian 

 series, known in the reports of the New York survey as the Potsdam sand- 

 stone. The location of the contact is in the neighborhood of the Choco- 

 late and Carp rivers. The underlying sandstone is highly inclined and is 

 "traversed by jjarallel east and west axes." On the uplifted edges of this 

 sandstone rest unconformably beds of the conglomerates and sandstones of 

 the red sandstone series, with very gentle northern dips. If the underlying 

 sandstone is Potsdam, then the red sandstones and conglomerates of Lake 

 Superior are post-Paleozoic. The author concludes, "from various points 

 of analogy between the red sandstone itself, its trappean dikes, and their 

 mineral associations with the similar components of the ]\Iesozoic or New 

 Red sandstone of the Atlantic States, that the formation in question is of 

 equivalent age and origin with this last-named interesting group of rocks." 



This contact w'as later described and pictured by Irving and other 

 geologists. Professor Rogers described its essential features well, but his 

 conclusion with regard to the age of the oveid3-ing rock is of course 

 valueless, since the imderlying sandstones are Algonkiaii, and not Cambrian. 

 Moreover, the overlying sandstones are not cut by trappean dikes. 



Locke, John. Report of Johu Locke to Dr. C. T. Jackson, describing tlie 

 observations made on tlie geology of the mineral lauds in Michigan. Dated October 

 27, 1847. ;iOth Congress, 1st session, lS-t7-4S. Senate Documents, VoL II, No. 2, 

 pages 183-199. 



By acts of March 1 and March 3, 184(!, the mineral lands of Lake 

 Superior were taken from the jurisdiction of the War Department and 

 placed under control of the General Land Office, at that time a branch 



